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Cogeneration at US dairies gets a boost from co-digestion

01/07/2012

While dairy farms are especially suited to CHP applications – the fuel is available locally and the process needs heat from the CHP unit to work – the sector’s potential is currently being overlooked in the US. Here Ed Ritchie reports on how the co-digestion of additional organic wastes is helping on-site biogas CHP to take off at US dairy farms.

A new dairy biogas project in New York has all the makings of a game changer for the struggling biogas industry for dairies in the US.

Anaerobic digestion of cow manure and food waste is not new to American dairies, but it is nowhere near its potential or the sector’s development in Europe. But with support from a variety of government agencies, thousands of dairies are more than ready to jump on the biogas bandwagon to exploit their untapped potential.

So can they replicate the recent success of Synergy Biogas? To secure the right political backing, the economics and environmental impact of the project have to be persuasive, and Synergy Biogas does more than fulfil those requirements. It Is the largest on-farm biogas-to-energy project in the state of New York, and the state’s first on-farm facility specifically designed for co-digestion.

The digester can handle up to 454,000 litres of recycled animal waste and food grade organic waste, creating enough biogas to run a 1.4 MW Jenbacher J420 biogas engine that can produce 10 GWh per year, plus a thermal output of 0.73 W/h – enough energy for about 1000 homes. It also reduces the dairy’s greenhouse gas emissions by about 8500 tonnes of carbon dioxide annually (equivalent to the emissions from 1700 automobiles).

SYNERGY BIOGAS AT NEW YORK DAIRY FARM

With 2,000 cows, Synergy Dairy is a dairy co-operative in Wyoming, NY, one of many agriculturally based communities across the state. But Synergy Biogas is independently owned and operated by CH4 Biogas, Atlantic Beach, FL.

Paul Toretta, Bob Blythe, and anaerobic digester manufacturer, Bigadan (Denmark) established CH4 Biogas in 2008 in response to market demand for anaerobic digestion and alternative energy in the US. The company has exclusive rights to market, supply, manufacture, install and use Bigadan technology in the US.

The environmental benefits made a strong argument for winning the government support that was vital to the project’s success, said Paul Toretta. ‘This is a big environmental play,’ he says. ‘First of all you’re diverting cow and industrial waste which would have gone on to the land and released methane. And we’re replacing fossil fuel so that makes for a more sustainable farm.’

Even with attractive environmental benefits, securing the grants and incentives was a daunting task, adds Lauren Toretta, vice president, CH4 Biogas. ‘It requires a lot of documentation and paperwork and can be very costly and time consuming. We had lots of support from the state and particularly from Senator Schumer. Even a year ago we were talking with him about applying for a grant and he wrote a letter on our behalf and he’s been helpful in our work with National Grid so we could meet the deadline requirements.’

National Grid is the state’s largest electricity utility, and its help was needed to upgrade a substation and the transmission lines to the Synergy operation. ‘The interconnection is the big issue,’ notes Paul Toretta. ‘When you’re out there in a rural area and you have to upgrade all the way back to the substation, it’s millions of dollars to get the grid upgraded.’ About 90% of the electricity produced is sold to National Grid, and the utility provided a US$750,000 grant through the company’s Renewable Energy and Economic Development Program to finance a new substation. Other financial incentives include $1 million from the New York State Energy Research and Development Authority (NYSERDA), and a 30% investment tax credit under the federal Energy Policy Act of 2005.

National Grid also funded a monitoring study operated by the PRO-DAIRY Program, Cornell University, NY. According to Curt Gooch, environmental systems sustainability engineer with the programme, the Synergy project is important from many aspects. ‘There are others that are doing co-digestion but not at this scale so it’s a great project that exemplifies what can be done,’ says Gooch. PRO-DAIRY is monitoring and reporting on the performance of three main components: first, the efficiency of converting the biomass gas; second, the utilization of the biogas and the efficiency of the engine and generators; and third, the economics.

BIOGAS SCHEMES ACROSS THE US

Past case studies from PRO-DAIRY can be found at: www.manuremanagement.cornell.edu. For example, Gooch cites Patterson Farms, a dairy farm located in Auburn, NY, as an interesting demonstration of the value of monitoring a co-digestion operation. In 2008, the farm installed an anaerobic digester to treat manure from about 1800 animals and food processing waste from 360 mature cow equivalents. The digester also takes in whey waste from a cream cheese factory.

The study notes that the food waste is high in energy, providing almost three times more energy per unit of mass than manure, and profitable because charging tipping fees for accepting food waste gives the dairy a new cash flow. Power generated on-site is used on the farm or exported back to the local utility via a net metering arrangement. Waste heat maintains the digester between 32ºC and 38ºC. Separated manure solids from the digester are also used for animal bedding.

Savings on animal bedding can be surprisingly high, notes Chris Noble, a member of the Synergy Dairy management team. ‘The digester runs the effluent to a system that separates solids from the liquid and that is a sterile inert material which we can use as bedding in the stalls of the barns,’ says Noble. ‘It reduces the need for us to buy sawdust or other bedding materials and the savings are in the neighbourhood of $100,000 a year.’

The CHP system can also be controlled remotely Photo: Ed Ritchie

Odour reduction is another benefit of anaerobic digestion, adds Noble. Complaints about the dairy’s smell have all but disappeared. Noble now looks forward to expanding Synergy’s operations to supply a growing demand for its dairy products. Expansion will lead to more land application of the sterile material as fertilizer. Although transporting the material makes it too costly at this point to sell, future plans include sales to cities as compost or fertilizer.

It is a different situation for the Big Sky West Dairy in Gooding, ID, where the digester produces 26,000 m3 of ammonia-free fibre that is sold at retail as a landscape fertilizer. The going rate for compost is about $3 a cubic yard (0.76 m3), but Big Sky’s digested fibre sells for two to three times that price, says project manager Bob Joblin.

Big Sky started its digester project when Dean Foods Company and AgPower Partners (DF-AP) joined with Big Sky West Dairy to develop a manure digester system funded only by private sector financing. The project relied on experts to secure financing, operate the digester and sell the energy to utility companies, without risk to the dairy producer. Cow manure plus organic waste from a local retailer fuels the co-digestion for enough biogas to generate 1.2 MW of electricity, which is sold to Idaho Power. Leveraging its experience, DF-AP has worked with the Innovation Center for US Dairy and EPA AgStar to share results and lessons learned with the industry.

SPREADING THE CO-DIGESTION MESSAGE

Such success stories are another sign that the co-digestion method is gaining traction, and PRO-DAIRY Progam’s Gooch sees policy changes at the state level as another positive step. Moreover, the potential marketplace is large. ‘This is a bud waiting to blossom because there are over 5000 dairy farms in New York State, but only 20 currently have digesters, and only nine use co-digestion,’ says Gooch. ‘So there’s a lot of room for growth. Synergy would be in the category of the upper 5% in size, but there are a lot of decent sized farms that would be great candidates for digesters if things make sense from a business standpoint. For this to happen a lot of effort would have to focus on streamlining the process. Our main goal is to create unbiased information for people to use in making business decisions.’

The Synergy project has already advanced the industry, says Paul Toretta. ‘It’s definitely helped us. And right now we’re in construction on a project in Ohio, and others in New York, where we’re in the development stage on two other projects with dairy and food waste,’ says Toretta. ‘At Synergy the ratio is about 40% food to 60% manure, but in Ohio it will be almost entirely food waste that we’re diverting from landfills and food manufacturers that would rather not send the waste of landfills.’ Sustainability and economics are the key factors in diverting food waste from landfills. But 23 states currently ban yard waste from landfills, and similar attempts to enact laws to ban food waste are gaining visibility in many states.

Banning organic waste from landfills is a common practice in Europe, says Karsten Buchave, CEO of Bigadan, and provides another selling point for anaerobic digestion

Bigadan’s engineering team developed the first mixed waste biogas plant in Denmark in 1984. To date, it has supplied 40 facilities worldwide, but the US is unique in many aspects. ‘The US is the biggest single market right now for biogas and there’s a lot of potential,’ says Buchave. ‘The size of the farms make it more attractive because there are many big farms in the US rather than over here, where most projects depend on collecting material with trucks. So there is a lot of cost associated with transportation as opposed to having the material right next to the receiving tank. That’s why it’s economically viable to make a product in the US even though the power prices are so much lower than over here. But thanks to good logistics we can save money in hauling so it’s still viable.’

Bigadan shipped a complete digester system to Synergy, but taking advantage of local suppliers could further improve the economics. Buchave also expects growing political support for renewable energy and higher fossil fuel prices to boost the anaerobic digestion industry. ‘It will help make it viable for us to invest in pre-treatment, and high-tech solutions at these facilities. We’re working on improving the digestion of heavier degradable organic compounds in the manure, such as lignin and cellulose. This is one of the areas where there is a lot of research in Europe, to get more power from each tonne of material.’

US SUPPORT FOR BIOGAS

Support for renewable energy with biogas is a major goal of the US Department of Agriculture (USDA). In March, the agency launched Got Manure? – a conference to recognize New York state’s growing importance in anaerobic digestion and to explore anaerobic digestion’s role in integrated manure management systems by taking a whole-farm approach. Attendees also heard about current issues and opportunities in the sector.

The 1.4 MW CHP unit is based on a Jenbacher gas engine Photo: Ed Ritchie

The launch took place at the Cayuga County Soil and Water Conservation District Community Digester in Auburn and was followed by a tour of the digester. In 2005, USDA Rural Development provided a $500,000 grant to the Cayuga County Public Utility Service Agency for the digester. It was a co-operative effort by the Cayuga County Soil and Water Conservation District and the Cayuga County government. The equipment processes manure from 1500 dairy cows and produces electricity and heat to supply county facilities adjacent to the digester site.

Overall, the USDA has taken a strong role in funding bio-digestion. In October 2011, the agency’s latest round of funds was designated for anaerobic digester projects in eight states, ‘to encourage renewable energy production, reduce energy costs and reduce greenhouse gas emissions and farm-based pollution’. The size of the financial assistance can be significant, as in the case of Farm Power Tillamook, the recipient of a $2.65 million loan and a $100,000 grant. In total funds for 2011, the programme provided nearly $21 million in assistance for bio-digesters, and leveraged over $110 million in project development. Through its Value-Added Producer Grant programme, USDA provides planning grants of up to $100,000 and working capital grants of up to $300,000 for establishing a bio-digester.

If there is one thing the US has plenty of, it is government programmes, and it is not just the USDA that is interested in anaerobic digestion. Additionally, the Natural Resources Conservation Service offers financial and technical assistance through the Environmental Quality Incentives programme. But wait, there is also AgSTAR, an outreach programme jointly sponsored by the US Environmental Protection Agency, the USDA, and the US Department of Energy. AgSTAR encourages the use of biogas recovery technologies at confined animal feeding operations. And do not forget state sponsored programmes such as (NYSERDA).

If that’s not enough, in a somewhat odd turnabout of events that involves the price of a kW in Canada, the industry in the US is getting help from Agriculture and Agri-Food Canada, an agency that provides research and support to Canada’s agriculture industry. ‘They developed a technology based on the cold climate,’ explains Jean-François Hince, project manager at Bio-Terre Systems, located in Sherbrooke, Quebec. ‘Normally the temperature of an anaerobic digester that you would see in typical German technology, for example, is 37°C to 38°C. But we licensed the technology and the temperature of the anaerobic digester is 20°C to 25°C. By using a lower temperature operation we need less preparation energy to maintain the operation and in a cold climate like Canada that allows you to use less energy during winter operations.’

For a cogeneration system, the lower process temperatures add up to less heat diverted to the digester and more heat for livestock operations but, ironically, Canada’s low electricity prices are not conducive to cogeneration. ‘In Quebec it’s not economically feasible because electricity rates are about C$0.06 a kW from hydropower,’ says Hince. ‘Biogas cogeneration needs more than that but in the US we are producing electricity with biogas and it’s no problem. Also, farms in Quebec are quite small, but the US farm that we’re working with is much larger and the amount of biogas from the manure and food waste is five to six times higher. So we are producing electricity full time.’

FULL-TIME OPERATION AND MAINTENANCE

Keeping generators running full time brings the highest financial returns, and reliable engine generator sets that can handle the harsh chemicals in biogas are critical.

In the case of Synergy’s Jenbacher genset, the technology is based on years of performance that include harsh landfill and farm environments. ‘Everybody’s learning something new every day,’ says Michael Wagner, marketing director, GE Jenbacher, Austria. ‘But we have about 1500 engines worldwide running on biogas and we are investing a lot of money and technology to improve the efficiency and the output, and extend the service lifetime of the engine.’

Jenbacher customers have a wealth of maintenance and monitoring options, adds Wagner. ‘We offer long-term service agreements up to the lifetime of the equipment. And the controls over the last 10 or 15 years have made great strides.

‘All of our installations have the capability of remote control from the plant’s facility, but also it can be controlled and monitored directly at a remote location. So if a company has 20 locations it can control them from one central operation, and we provide the operator and customer with the opportunity to monitor and access his plant from our service centre for online help.’

With Jenbacher’s off-site monitoring and the fact that the genset components are containerized, the entire project is designed for easy installation and operation, as well as easy replication, says Paul Toretta.

‘The Bigadan technology is shipped in ISO containers with a modular design,’ he says. ‘You install it and tie it together and it’s just like your stereo system. It’s kind of plug and play and you build the same plant over and over again. Even the engine comes in a container so it can be described as plug and play.’

All told, the Synergy Biogas project symbolizes the financial and sustainability rewards of anaerobic co-digestion for fuelling an on-site cogeneration plant. We have seen that the project encountered its share of challenges related to connecting to the grid, but its developers have noted that future projects are benefiting from the dedication of the various parties involved.

With more than 8000 dairy and swine operations, it may be too early to say the US is on the path to reaching its biogas production potential. But all the signs are pointing in the right direction.